The invention relates to a finish for partially oriented polyester yarn. More specifically, the invention relates to a finish which enables texturing of partially oriented polyester yarn with a substantial decrease in broken filament levels in the resultant textured yarn. Additionally, the invention provides improved finishes for polyester yarns which are compatible with polyurethane texturing element and which minimize broken filament levels in the textured yarn.
False twist texturing of partially oriented polyester yarns involves heating of the yarns by means of a heater tube or plate and subsequently twisting the yarn by means of a friction disc, belt or spindle. Lubricating finishes are typically applied to the yarn prior to the texturing operation in order to prevent filament breakage and other damage to the yarn during texturing.
Broken filament levels are controlled by fiber-to-fiber friction at low speed. Normally this friction is reduced by viscous or solid lubricants with recognized "boundary lubricant" properties. For example, sodium stearate, isostearate or other high viscosity lubricants can be used to reduce broken filament levels. When texturing is conducted by means of elastomeric friction elements, e.g. polyurethane or polyacrylonitrile discs, or polyacrylonitrile/polybutadiene belts, as opposed to "hard" texturing elements such as ceramic discs, it is important that the finish not cause excessive wear of the elastomeric surface. Such excessive wear of elastomeric discs or belts can be attributed to impregnation of fiber finish into the disc or belt and/or chemical attack on the disc or belt surface by the fiber finish.
Though texturing finishes have been developed in recent years which have drastically reduced the amount of broken filaments, broken filaments are found in the textured yarns in measurable amounts and finishes capable of still further reducing the broken filament level would be highly desirable. Further, finishes capable of reducing broken filament levels while not increasing the propensity of the finish to degrade elastomeric texturing elements would likewise be highly desirable.